agree with jodi. You have set the stage for an open and honest relationship. I don't think you need to tell him who you are in love with unless something comes of it. It isn't really necessary unless it becomes necessary.
How did he react? Was he interested in the theory behind loving more than one? Did he ask questions? You and he could explore this together as you are both new to it... that is a good place to be... so much potential and room for growth without there being drama in your life.
Anyone want to be friends on Facebook?
Send me your name via PM